The present invention relates to a circular table for NC control table laid on a table of NC machine tool for performing a rotating or indexing operation of workpiece (hereinafter referred to as an NC circular table) and ail NC circular table apparatus.
FIG. 1 shows an example of an NC machine tool 2. The NC machine tool 2 has an NC controller 1. An NC circular table body 4 is laid on a table 7 of the NC machine tool 2. A connector 6 of a cable 8 provided on the NC circular table body 4 is connected to the NC controller 1. Incidentally, the same reference numerals are used to indicate the like members or components through the specification.
Also, the NC circular table body 4 is provided with a servo motor 9 for rotating a rotary table 14 on which the workpiece 10 is to be mounted and an encoder 3 for detecting a position for controlling the rotation of the rotary table 14. The encoder 3 is connected to the NC controller 1 through the above-described cable 8 and connector 6 and is controlled by a program installed in the NC controller 1.
By the way, encoders 3 are categorized into incremental type ones and absolute type ones.
In the incremental type encoder 3, when the power source is cut off, the current position (angular position of the rotary table 14) of the workpiece 10 is unknown. Accordingly, it is necessary to perform the original restoration work when a power stop caused by lightning or the like. Thus, this type encoder suffers from the problem that it takes a long time for the restoration.
On the other hand, the absolute type encoders 3 are subclassified into a mechanical system for storing the current position or the original position by a mechanical means such as a gear (hereinafter referred to a mechanical type) and a backup battery system for storing the current position or the original position in terms of absolute positions by a backup battery (hereinafter referred to a backup battery type). Thus, the absolute type encoders 3 have a merit that the original restoration work may be dispensed with even if the power source is cut off. However, the mechanical type encoders 3 suffer from the problem that the entire system is large in size and complication in structure. Therefore, in general, the backup battery type encoder that may miniaturize the overall system has been extensively used.
However, in case of the conventional backup battery type encoder, in the above-described NC machine tool 2, as shown in FIG. 2, the backup battery 5 of the encoder 3 is provided within the NC controller 1. Thus, this system has the following disadvantages.
In general, the NC circular table body 4 is separated from the NC controller 1 upon the delivery from the factory until it is installed at the working field. Also, even after the installing of the NC circular table body 4 at the working field, there is a necessity that the NC circular table body 4 be dismounted from the NC machine tool 2 and separated away from the NC controller 1, for example, due to the change of the workpieces 10. Also, in the case where a plurality of NC circular table bodies 4 and a plurality of NC machine tools 2 are used in combination, there is a possibility that the combination of the NC circular table body 4 and the NC machine tool 2 is changed. In these cases, the encoder 3 of the NC circular table body 4 is not supplied with electric power from the power source by the backup battery 5 within the NC controller 1 so that the original position or the current position becomes unknown. Thus, even if the system is of the absolute type, it is necessary to carry out the original restoration work, disadvantageously.
An object of the present invention is to provide an NC circular table and an NC circular table apparatus that are superior in practical use and workability to dispense with the original restoration operation in an absolute type encoder using a backup battery.
According to the present invention, an NC circular table is used to an NC machine tool having an NC controller for performing a positional detection by an absolute type encoder, and a backup battery for the encoder is provided to an NC circular table body.
Also, an NC circular table used to an NC machine tool having an NC controller for performing a positional detection by an absolute type encoder is characterized in a backup battery for the encoder is provided inside or outside of at least one of an NC circular table body, a cable connected to the NC circular table body and a connector connected to said NC circular table body.
Also, in the NC circular table according to the first aspect of the invention, a connector that may connect the encoder detachably to the NC controller is provided in the NC circular table body.
Also, in the NC circular table according to either first aspect or second aspect, the NC circular table body is detachable from the NC controller.
Also, an NC circular table used to an NC machine tool having an NC controller for performing a positional detection by an absolute type encoder to which a backup battery is connected, and in which the NC controller and a cable connected to an NC circular table body are detachable away from each other, is characterized in that a backup battery for the encoder is provided inside or outside of at least one of the NC circular table body, the cable connected to the NC circular table body and a connector connected to the NC circular table body, and the electric supply from the backup battery to the encoder is not interrupted by the separation between the NC controller and the cable connected to the NC circular table body.
Also, an NC circular table apparatus used to an NC machine tool having an NC controller for performing a positional detection by an absolute type encoder, comprises an NC circular table to which a cable for connecting the NC controller and an NC circular table body with each other is detachable, and a backup battery device provided with a backup battery connected to the NC circular table body for feeding electricity to the encoder of the NC circular table body when the cable that has connected the NC controller and the NC circular table body with each other is removed.
Also, in this case, in the NC circular table apparatus, the backup battery device is connectable to at least one of a connector for connection with the cable provided to the NC circular table body and a connector of the cable connected to the NC circular table body.
Since the data such as an original position or a current position within the encoder are preserved by the backup battery provided in the NC circular table body, it is unnecessary to perform the original restoration operation even if the separation and reconnection of the NC circular table body and the NC controller. Again, it is possible to perform the machining work of the workpiece by the NC circular table body.
Also, for instance, in the case where the NC controller and the NC circular table body are connected to each other through the detachable cable, even if the NC controller and the NC circular table body are separated apart from each other, the electric supply is ensured by a capacitor or the like within the encoder to back up the data such as an original position or a current position within the encoder for a while. In the meanwhile, the backup battery device is connected to the NC circular table body and the electricity is fed from the backup battery provided in the backup battery device to the encoder of the NC circular table body so that the data such as an original portion or a current position within the encoder may be preserved continuously.
With such an arrangement, as described above, it is possible to provide an NC circular table and an NC circular table apparatus that are superior in practical use or workability that may dispense with the original restoration operation.